2,4-Dichloro-5-fluoro­benzoic acid

In the title compound, C₇H₃Cl₂FO₂, the dihedral angle between the carboxyl group and the benzene ring is 49.27 (13)°. In the crystal structure, inversion dimers arise via pairs of weak O—H...O hydrogen bonds (H...O = 2.23 Å).

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.052
• wR factor = 0.142
• Data-to-parameter ratio = 14.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT230_ALERT_2_C Hirshfeld Test Diff for    O2     -   C1      ..       6.82 su
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C1

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The title compound, (I), is an important intermediate in the syntheis of fluoroquinolone antibiotics (Li & Guo, 1992). We report herein its structure (Fig. 1).

The bond lengths and angles in (I) are within normal ranges (Lalancette et al., 1996; Potrzebowski & Chruszcz, 2007; Taga et al., 1985). The carboxyl group and phenyl ring planes are twisted by 49.27 (13)°, which is caused by steric effects between carboxylic group and ortho-chlorine atom. In the crystal, a weak O—H···O hydrogen-bond between inversion related carboxyl groups is formed (Table 1) resulting in an R²₂(8) ring.

Related literature

For related structures, see: Lalancette et al. (1996); Potrzebowski & Chruszcz (2007); Taga et al. (1985). For the synthesis, see: Tang et al. (1991). For background, see Li & Guo (1992).

S2. Experimental

The title compound was prepared from 2,4-dichlorofluorobenzene according to the reported method (Tang et al., 1991). Colourless plates of (I) were obtained by slow evaporation of an aqueous solution at room temperature.

S3. Refinement

H atoms were placed at calculated positions and refined in the riding-model approximation, with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C), and O—H = 0.82 Å and U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. The structure of (I), with displacement ellipsoids drawn at the 30% probability level for the non-hydrogen atoms.

2,4-Dichloro-5-fluorobenzoic acid

Crystal data

C7H3Cl2FO2	F(000) = 416
Mr = 208.99	Dx = 1.672 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1959 reflections
a = 5.0438 (19) Å	θ = 2.3–26.7°
b = 10.632 (4) Å	µ = 0.75 mm^−1
c = 15.550 (6) Å	T = 295 K
β = 95.515 (5)°	Plate, colorless
V = 830.0 (5) Å^3	0.35 × 0.12 × 0.06 mm
Z = 4

Data collection

Bruker SMART APEX CCD diffractometer	1540 independent reflections
Radiation source: fine-focus sealed tube	1293 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.056
φ and ω scans	θmax = 25.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2002)	h = −6→6
Tmin = 0.779, Tmax = 0.956	k = −12→12
5973 measured reflections	l = −18→18

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.142	w = 1/[σ^2(Fo^2) + (0.0612P)^2 + 0.7105P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
1540 reflections	Δρmax = 0.61 e Å^−3
110 parameters	Δρmin = −0.37 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.151 (12)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.5167 (5)	0.9568 (3)	0.36752 (18)	0.0333 (7)
C2	0.5453 (5)	0.9186 (3)	0.27613 (17)	0.0304 (6)
C3	0.3990 (6)	0.8225 (3)	0.23460 (18)	0.0339 (7)
C4	0.4315 (7)	0.7892 (3)	0.1506 (2)	0.0443 (8)
H9	0.3323	0.7236	0.1242	0.053*
C5	0.6115 (7)	0.8534 (3)	0.1059 (2)	0.0481 (9)
C6	0.7558 (7)	0.9497 (3)	0.1461 (2)	0.0468 (8)
C7	0.7278 (6)	0.9821 (3)	0.2299 (2)	0.0389 (7)
H7	0.8306	1.0466	0.2561	0.047*
O1	0.2963 (4)	0.9777 (2)	0.39280 (13)	0.0423 (6)
O2	0.7417 (5)	0.9684 (3)	0.41719 (17)	0.0760 (10)
H1	0.7099	0.9894	0.4659	0.114*
F1	0.9320 (5)	1.0123 (2)	0.10281 (14)	0.0758 (8)
Cl1	0.17719 (18)	0.73365 (8)	0.28805 (5)	0.0506 (4)
Cl2	0.6602 (3)	0.81275 (13)	0.00154 (6)	0.0861 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0266 (14)	0.0421 (16)	0.0310 (15)	−0.0001 (12)	0.0018 (11)	−0.0062 (12)
C2	0.0286 (14)	0.0331 (15)	0.0294 (14)	0.0048 (11)	0.0024 (11)	−0.0023 (11)
C3	0.0369 (15)	0.0327 (15)	0.0320 (15)	0.0015 (12)	0.0035 (12)	0.0039 (12)
C4	0.058 (2)	0.0380 (17)	0.0367 (17)	−0.0063 (15)	0.0041 (14)	−0.0066 (13)
C5	0.066 (2)	0.0504 (19)	0.0286 (16)	0.0005 (17)	0.0110 (15)	−0.0039 (14)
C6	0.0483 (19)	0.053 (2)	0.0417 (18)	−0.0052 (15)	0.0167 (15)	0.0051 (15)
C7	0.0362 (16)	0.0397 (16)	0.0417 (17)	−0.0039 (13)	0.0085 (13)	−0.0061 (13)
O1	0.0242 (11)	0.0667 (15)	0.0365 (11)	0.0027 (9)	0.0053 (8)	−0.0130 (10)
O2	0.0477 (16)	0.129 (3)	0.0509 (16)	0.0006 (16)	0.0015 (12)	−0.0256 (16)
F1	0.0881 (17)	0.0890 (17)	0.0564 (14)	−0.0316 (14)	0.0390 (12)	−0.0013 (12)
Cl1	0.0604 (6)	0.0461 (5)	0.0470 (5)	−0.0165 (4)	0.0143 (4)	0.0011 (3)
Cl2	0.1285 (11)	0.0979 (9)	0.0369 (6)	−0.0234 (7)	0.0330 (6)	−0.0179 (5)

Geometric parameters (Å, º)

C1—O1	1.234 (3)	C4—H9	0.9300
C1—O2	1.316 (4)	C5—C6	1.371 (5)
C1—C2	1.498 (4)	C5—Cl2	1.720 (3)
C2—C3	1.383 (4)	C6—F1	1.342 (4)
C2—C7	1.395 (4)	C6—C7	1.368 (4)
C3—C4	1.378 (4)	C7—H7	0.9300
C3—Cl1	1.736 (3)	O2—H1	0.8200
C4—C5	1.377 (5)
O1—C1—O2	123.3 (3)	C3—C4—H9	120.2
O1—C1—C2	121.5 (2)	C6—C5—C4	119.2 (3)
O2—C1—C2	115.2 (2)	C6—C5—Cl2	120.0 (3)
C3—C2—C7	117.8 (3)	C4—C5—Cl2	120.8 (3)
C3—C2—C1	123.2 (3)	F1—C6—C7	119.1 (3)
C7—C2—C1	119.1 (2)	F1—C6—C5	119.3 (3)
C4—C3—C2	121.7 (3)	C7—C6—C5	121.6 (3)
C4—C3—Cl1	117.0 (2)	C6—C7—C2	120.1 (3)
C2—C3—Cl1	121.2 (2)	C6—C7—H7	119.9
C5—C4—C3	119.6 (3)	C2—C7—H7	119.9
C5—C4—H9	120.2	C1—O2—H1	109.5
O1—C1—C2—C3	−49.8 (4)	C3—C4—C5—C6	0.1 (5)
O2—C1—C2—C3	131.5 (3)	C3—C4—C5—Cl2	179.1 (3)
O1—C1—C2—C7	130.3 (3)	C4—C5—C6—F1	179.8 (3)
O2—C1—C2—C7	−48.5 (4)	Cl2—C5—C6—F1	0.8 (5)
C7—C2—C3—C4	0.4 (4)	C4—C5—C6—C7	1.0 (5)
C1—C2—C3—C4	−179.6 (3)	Cl2—C5—C6—C7	−178.0 (3)
C7—C2—C3—Cl1	177.3 (2)	F1—C6—C7—C2	179.8 (3)
C1—C2—C3—Cl1	−2.7 (4)	C5—C6—C7—C2	−1.3 (5)
C2—C3—C4—C5	−0.8 (5)	C3—C2—C7—C6	0.6 (4)
Cl1—C3—C4—C5	−177.8 (3)	C1—C2—C7—C6	−179.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1···O1^i	0.82	2.23	3.034 (3)	167

Symmetry code: (i) −x+1, −y+2, −z+1.